1. Field of the Invention
The present invention relates to a rechargeable battery. More particularly, the present invention relates to a rechargeable battery having an improved gasket structure.
2. Description of the Related Art
Unlike a primary battery that is incapable of being recharged, a rechargeable battery is a battery that can be repeatedly charged and discharged. A low capacity rechargeable battery having a single cell has been used in small portable electronic apparatuses, such as mobile phones, laptop computers, and camcorders. A high capacity rechargeable battery that includes a plurality of cells connected to each other in a pack is used as a power source of a motor of a hybrid electric vehicle or the like. The rechargeable batteries are manufactured in various shapes, for example a cylindrical shape or a box shape.
The rechargeable batteries are connected in series so as to be used for driving a motor of an electric vehicle, which requires large power, thereby forming a high capacity rechargeable battery module.
A rechargeable battery includes an electrode assembly, in which an anode and a cathode are disposed with a separator interposed therebetween, a case that has a space, which accommodates the electrode assembly, and a cap assembly that closes and seals the case.
When the rechargeable battery has a cylindrical shape, uncoated regions, where an active material is not coated, are formed in the anode and the cathode of the electrode assembly. The anode uncoated region and the cathode uncoated region are disposed to face different directions from each other.
A cathode current collecting plate is attached to the cathode uncoated region, and an anode current collecting plate is attached to the anode uncoated region. The cathode current collecting plate is electrically connected to the case, and the anode current collecting plate is electrically connected to the cap assembly. Accordingly, the case serves as a cathode terminal, and a cap plate provided in the cap assembly serves as an anode terminal.
Therefore, the cap assembly and the case need to be electrically insulated. For this reason, a gasket is provided between the cap assembly and the case.
The anode current collecting plate and the cap assembly are electrically connected to each other by a lead member formed of a conductive metal. The anode current collecting plate and the cap assembly are welded to the lead member and then inserted into the case. After the cap assembly is inserted into the case, the cap assembly is clamped and fixed to the case.
The gasket not only electrically insulates the cap assembly from the case, but seals the case. For this purpose, during a clamping process, uniform pressure is applied to the gasket. However, during the clamping process, it is difficult to apply uniform pressure to the gasket, which causes the case to be inappropriately sealed. As a result, an electrolyte may leak. If the electrolyte leaks, charging and discharging efficiency deteriorates. Further, there is a risk of explosion due to a short circuit. In addition, in the cylindrical battery, since the cap assembly is cylindrical, the cap assembly may rotate with respect to the case. If the cap assembly rotates with respect to the case, a defective electrical contact may occur between the lead member and the cap assembly. The defective electrical contact causes an increase of resistance in a contact portion, which causes heat generation and output power deterioration. When the cap assembly extremely rotates, a welded portion between the lead member and the cap assembly may be separated. In this case, charging and discharging cannot be performed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.